More Water Headed for Parched Plains States

May 16, 2013 by Justin Leighty
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The Northeast and Central Appalachians: A potent storm system brought moderate to heavy precipitation to most of the region. Between 2 and 5 inches fell on many locations in central and eastern West Virginia, the Maryland Panhandle, central and eastern Pennsylvania, New Jersey, southeastern New York and central Maine. Generally 0.5 to 2.0 inches fell elsewhere, with lesser amounts reported in the upper Hudson Valley and northern Vermont.

This precipitation eased abnormal dryness in many areas to the south and west of New York City. D0 persisted across interior eastern Pennsylvania and in parts of the Appalachians where 30-day totals remained two-thirds of normal or less, and a small area of D1 remained near the West Virginia Panhandle. Across eastern New York and New England, only a few spots in extant D0 to D1 conditions improved outside central Maine. Much of eastern New York and New England to the south and west of central Maine has recorded 2 to 5 inches less precipitation than normal over the last 90 days.

Southeast: In Florida, between 1 and 3 inches of rain fell near Lake Okeechobee, easing abnormal dryness in a small area northwest of the Lake. Farther north, similar amounts were recorded along the Gulf Coast of northern Peninsula, shaving off the northern tier of the small D2 area.

Across other areas of the Florida Peninsula and in eastern North Carolina, only a few tenths of an inch fell at best. As a result, existing dryness and drought persisted, and abnormal dryness was expanded through northeastern North Carolina and adjacent southeastern Virginia. The D0 and D1 areas in the Southeast generally received 50% to 75% of normal precipitation during the first 4 1/2 months of the year, and 90-day totals are 3 to 6 inches below normal in northwestern parts of the Florida Peninsula.

The Northern Half of the Plains and the Upper Mississippi Valley: Beneficial precipitation – generally 0.5 to 2.0 inches – fell on portions of southwestern Minnesota, southeastern South Dakota, west-central Iowa, and parts of southern and eastern Nebraska, with up to 3 inches reported in a few spots from central Iowa westward to the Omaha, Neb., area. As a result, former D0 to D2 conditions improved by one category where the larger amounts were measured. Elsewhere, only isolated locations reported more than a few tenths of an inch. D0 expanded to cover southeastern North Dakota, and dryness and drought remained essentially unchanged elsewhere.

The Southern Half of the Great Plains: Precipitation totals varied widely this week, even within small distances in some cases. At least a few tenths of an inch fell on most sites in central and eastern Kansas, west-central Kansas, central and northern Oklahoma east of the Panhandle, the eastern Texas Panhandle, and most of Texas south of a line from Longview to Dallas to east of San Angelo. Within these areas, some locations received moderate to heavy amounts. More than 2 inches soaked many locations in central and southeastern Texas, with some reports topping 5 inches in areas from north of Houston to southern Louisiana. More than 2 inches also fell on many locations in southern Texas and in small areas across the east-central Texas Panhandle, northeastern and north-central Oklahoma, and north-central and west-central Kansas. In contrast, only light precipitation, if any, fell on northwestern and southwestern Kansas, the Oklahoma Panhandle, the western Texas Panhandle, the Big Bend region of Texas, and most of the Red River Valley.

Predictably, this precipitation pattern resulted in an array of small-scale Drought Monitor adjustments, but some broader changes can be generalized. Dryness and drought eased significantly in the wetter areas of southeastern and (to a lesser extent) far southern Texas. Many of the former D1 to D3 areas in northern Kansas also improved. On the other hand, D3 and D4 areas increased a bit along the Red River, and D0 to D1 conditions expanded from northeastern Texas into southwestern Arkansas and northwestern Louisiana. Since mid-February, precipitation deficits of 4 inches to locally over 8 inches have accumulated in northeastern Texas, the adjacent Red River Valley in Oklahoma, northwestern Louisiana, and southwestern Arkansas.

The Rockies Westward to the Pacific Coast: Moderate to heavy precipitation fell on central, east-central, and north-central sections of Colorado, with 2 to 4 inches reported near the middle of the state. As a result, the D2 to D4 areas in eastern Colorado retreated southward somewhat, and improvements to D0 and D1 were made in central and north-central parts of the state.

Light precipitation – at least a few tenths of an inch – was reported across much of southeastern Wyoming, western Colorado, eastern Utah, southeastern Idaho, the Sierra Nevada, and the southern Cascades while the rest of the region experienced a dry week.

The declining snowpack and substantially below-normal precipitation for the past 2 to 6 months led to some significant deterioration across the southwestern quarter of Montana and adjacent sections of Idaho. Most notably, a broad area of D3 was introduced in southwestern Montana where 20 to 50 percent of normal precipitation has been measured over the past 3 months. Some areas in this region have received only 40% to 65% of normal amounts since the start of the water year in October 2012. Meanwhile, D2 conditions in part of northeastern Utah were improved to D1 where deficits have declined during the past couple of months. Other areas were unchanged.

Hawaii, Alaska, and Puerto Rico: Recent wetness on the eastward-facing slopes of Maui has boosted streamflows and eased abnormal dryness. Dryness and drought continue on leeward parts of Maui, with severe to extreme drought covering the south side of the Island. On the Big Island of Hawaii, recent rainfall has improved pasture conditions in the lower South Kohala District, where D3 was improved to D2. Pasture improvements were also reported in the lower elevations of the Kona slopes, resulting in conditions easing to D0. Dryness and drought remained unchanged in other parts of the state. In Alaska, abnormal dryness and moderate drought remained unchanged as less than 0.3 inch of precipitation fell on central and northern parts of the state.

Looking Ahead: During May 16 – 20, heavy precipitation is forecast over a broad area covering the northern Rockies, the northern half of the Plains and the Upper Mississippi Valley. Generally 1.5 to locally 3.5 inches are anticipated in parts of Montana, across all of North Dakota and Minnesota, in all but southwestern South Dakota, and through adjacent sections of Nebraska and Iowa. Moderate amounts of at least 0.5 inch are expected from the eastern reaches of Kansas, Oklahoma, and northeastern Texas eastward through the mid-Atlantic and the Carolinas. One to two inches are possible in eastern Oklahoma, western Arkansas, and much of North Carolina and adjacent southeastern Virginia. In contrast, little or no precipitation is expected over the southwestern quarter of the country and across southern, western, and most of coastal Texas. Light amounts, locally approaching an inch, are expected elsewhere.

For the ensuing five days (May 21 – 25), the odds favor above-median precipitation across northern and western Alaska, the northern Great Plains, and the Eastern States north of Florida. In contrast, below-median precipitation appears likely across the central and southern Plains, and from the central Rockies northward through southern Montana and southeastern Idaho.